The present invention relates generally to fabric softener compositions with improved stability and softening. The present invention further relates to processes for preparing the same.
Fabric softener (i.e., conditioning) compositions are commonly used to deposit a fabric softening compound onto fabric. Typically, such compositions contain a cationic fabric softening agent dispersed in water. Fabric softener compositions used in the rinse cycle are generally separated into two basic product categories based on solids (active softening agent/fabric softening active) concentration. Compositions containing more than 10% by weight (e.g., 10-50% or 15-25% by weight) solids are often referred to as “concentrated” compositions, and compositions containing less than 10% by weight (e.g., 3-5% by weight) solids are often referred to as “diluted” compositions. Compositions containing softening agent below 5% by weight are sometimes called “ultra dilute,” while softening agent levels in the range of 5-10% by weight are sometimes called “semi-dilute.” Dilute, ultra dilute and semi-dilute fabric softener compositions, each of which are all considered low solids (or low active) compositions, usually have very low viscosity (with minimal or no thickening agents (viscosity control agents)) due to the low active concentration.
In most cases, however, the viscosity of a fabric softener commercial product has a significant influence on consumer perception, especially in regional markets like Europe, Central America, Latin America and the Far East. In a broad sense, consumers associate a high viscosity with good performance and product quality. For example, fabric softeners for the Mexican market typically have an active concentration of about 5-7% by weight, but require a viscosity of about 300-400 cps; fabric softeners for the Brazilian market typically have an active concentration of about 5% by weight, but require a viscosity of about 1500-2000 cps; fabric softeners for the European market typically have an active concentration of about 4-5% by weight, but require a viscosity of about 100-400 cps; fabric softeners for the Philippines market typically have an active concentration of about 3-7% by weight, but require a viscosity of 500-700 cps; while fabric softeners for the China market typically have an active concentration of about 3-5% by weight, but require a viscosity of about 800-1500 cps. Unless otherwise indicated, the viscosity numbers in the present application can be obtained by a Brookfield RV model viscometer at 25° C. A person familiar with the field of the present application will understand that other equipment achieving the same outcomes for measurement purposes are within the spirit and scope of the present application.
Various additives have been used in fabric softener compositions in order to achieve the desired high viscosity. For example, polymeric thickening agents, such as starches and cellulose ethers, have been commonly used to increase the viscosity of low solids fabric softener compositions. However, these conventional viscosity control agents are expensive. Further, such agents are typically included at levels in the range of from about 0.05% to about 1% by weight, which in turn increases the cost of the resultant fabric softener compositions. Moreover, conventional polymeric thickening agents tend to generate a drop in viscosity in the fabric softener product during storage. Typically, such end products containing polymeric thickening agents require a separate gelatinization stage, in which they are mixed with water. This can increase the complexity and expense of the manufacturing process. Finally, conventional polymeric thickening agents typically do not add significant benefits to the overall softening performance of the end product. There is therefore a strong demand for a low solids, high viscosity fabric softener composition that has minimal or no polymeric additives.
U.S. Pat. No. 6,878,684 (Unilever Home & Personal Care USA, Greenwich, Conn.) discloses a fatty acid partial ester of a polyhydric alcohol that may act as a viscosity modifier, if the fabric conditioning composition containing a quaternary ammonium compound (“quat”) is manufactured under certain conditions. The reference appears to describe that it is necessary to expose the fabric conditioning composition to shear at a temperature below the phase transition temperature of the quaternary ammonium compound.
In the present application, a quaternary ammonium compound or salt, or a derivative thereof may be generally referred to as a quat. An ester-containing quaternary ammonium compound or salt is sometime referred to as an ester quat. A quaternized amine may be referred to as an amine quat or quat of the amine, which can be, for example, a quaternized alkyl amine, a quaternized alkyl amido amine, or a quaternized ammonium polyamine. More information about quats, ester quats, and amine quats, especially about those that can be used for the present technology, is provided in the detailed description below.
U.S. Pat. No. 6,525,016 (Goldschmidt Chemical Corporation, Hopewell, Va.) discloses a high viscosity, low solids rinse cycle fabric softener formulation that includes a homogenous blend of (a) 50-90% by weight of at least one imidazolinium quaternary ammonium compound; and (b) 10-50% by weight of at least one amido amine quaternary ammonium compound. The reference appears to require that the at least one imidazolinium quaternary ammonium compound and the at least one amido amine quaternary ammonium compound be free of any unsaturated alkyl groups.
U.S. Pub. Pat. App. No. 2002/0187911 (Goldschmidt Chemical Company, Hopewell, Va.) discloses a high viscosity, low solids fabric softener formulation that uses at least one amine ethoxylate having the formula (R(nEO))sNHt, wherein R is a saturated or unsaturated, linear or branched alkyl group containing from 10 to 22, preferably from 12 to 18, carbon atoms; EO is ethoxylate; n is the number of moles of EO and is from 1 to 10, preferably from 2 to 5; s=1, 2, or 3; t=1, 1, or 2; and s+t=3, to enhance the viscosity of the composition without the use of polymeric thickening agents. The addition of the amine ethoxylate to the low solids fabric softener composition is alleged to not only enhance the viscosity, but also the softening performance, of the composition.
EP1254203B1 (Unilever PLC, United Kingdom) discloses a fabric conditioning composition that uses a stabilizing system containing at least one salt of a multivalent inorganic anion or non-sequestering multivalent organic anion to allegedly improve the viscosity of the conditioning composition. A mixture comprising sodium chloride and sodium sulfate is described as being preferably used. Additionally, there is at least one salt of a univalent anion in the mixture.
WO 97/08285 (Colgate/Palmolive Company, New York, N.Y.) discloses the use of fatty acid esters of mono or polyhydric alcohols as emulsion or dispersion stabilizers in fabric softening compositions containing 3-40% by weight of a fabric softener combination comprising an amido tertiary amine and an ester quat material. The weight ratio of the fabric softener combination to the fatty acid ester(s) of mono or polyhydric alcohol is in the range of from about 40:1 to about 5:1, while the level of the fatty acid ester(s) of mono- or polyhydric alcohol in the composition is in the range of from about 0.2% to about 2% by weight.
GB 2204608 (Kao Corporation, Japan) discloses liquid softener compositions containing a quaternary ammonium salt, a polyamide and an ester derived from a fatty acid having 10-24 carbon atoms and glycerol. The weight ratio of quaternary ammonium salt to ester is described as being in the range of from about 0.1:1 to 3:1.
JP 63-295764 (Kao Corporation, Japan) discloses soft finishing agents containing (a) a cationic textile softening substance, (b) a straight chain fatty acid and (c) an esterified product of fatty acid and glycerol. The molar ratio of (b):(a) is 0.001 to 0.2, the weight ratio of (b):(a) is 0.01 to 3, and the total amount of (a), (b) and (c) is 3 to 20 weight percent.
DE-A1-4400927 (Henkel, Germany) discloses aqueous solutions of quaternized fatty acid triethanolamine ester salts thickened by adding 0.01 to 0.1 wt % of esters of fatty acids with commercial oligoglycerol mixtures.
GB 1599171 (Procter & Gamble, Cincinnati, Ohio) discloses an aqueous textile treatment composition comprising a water insoluble cationic fabric softener, a water insoluble nonionic fabric softener, and from 0.1 to 10 wt % of an aromatic carboxylic acid. The nonionic fabric softener is present in an amount from 0.5 to 12 weight percent.
However, in light of the references noted above, there still remains a strong demand and unresolved need for a low solids, high viscosity fabric softener composition that contains minimal or no polymeric additives, exhibits improved softening, stability and viscosity performance properties as desired in different regions of the world, and is cost-effective to manufacture.